C900 PC 150 vs PC 200

[z8e]

Hello All,

A few years back, a local civil engineer convinced the municipality here to require PC 200 for water lines instead of PC 150. The rationale was that as temperature of the pipe increased, hoop strength decreased, and in the case of PC 150, might decrease to the point of failure at the joints.
With that as background, I'm taking a poll. What do the jurisdictions you work with specify, and what is the basis for what they require?

 

[rconner]

The AWWA pvc pressure classes now do not mean the same as they did for more than a quarter century (before a standards revision not long ago -- you should be aware of the history that was explained in the thread

http://eng-tips.com/viewthread.cfm?qid=227976

). The practical safety factor has been reduced.

 

[jgailla]

z8e,
As rconner obliquely references, you should be using DR14, 18, and 25 instead of PC200, 150, and 100.

Regardless of the AWWA changes, I still use the 100, 150, and 200 psi in PVC pipe design for potable water and wastewater pressure piping.

I have designed potable water lines in the 4" to 20" range under several municipalities in flatland Florida and Georgia. Generally, they require DR25 for transmission. On site water lines, I typically use DR18 to accommodate fire pumping used at FDCs.

The federal Unified Facilities Criteria (old Technical Manuals) require 150 psi minimum for water mains.

Only one municipality required DR14 on sites for fire pumping issues, but I believe they were confused as to what design pressures were required on site. They were the stupidest municipality I worked with.

 

[cvg]

most of the municipalities I have worked with don't allow PVC for transmission and distribution mains. Typically require DIP, CML&C or concrete steel cylinder pipe, 150 psi design pressure minimum

 

[jgailla]

What area are you in, cvg?
I have designed in Florida and southern Georgia and reviewed many other local design standards in California, Arkansas, Arizona, Mississippi, South Carolina, Texas, and North Carolina.
I don't recall a utility company during these reviews banning PVC under 24", although I've only looked at one or two local utility standards in each state mentioned.

 

[cvg]

southwest
I have done one project in SoCal using PVC

 

[jgailla]

cvg,
Do you think there are soil and/or climate issues with PVC in the southwest, or just regional/historical preference? Maybe both?

 

[coloeng]

I am in Colorado and the two water districts I have worked for base their requirements on the DR instead of pressure class. They used DR18 for pressures up to 150 and DR14 for pressures above 150. As rconner indicated, the standard was changed a few years back and some engineers, myself included, aren't comfortable with the reduction in practical safety factor of the new standard. That is why we specify the C900 pipe based on DR instead of pressure class.

With over 20 years of C900 use in one of the systems, there were no major problems using C900. The other system hasn't been around long enough to know if there are issues, but other systems in the same area have been specing C900 for years with no major problems.

 

[cvg]

I think there are a mix of both geotechnical factors as well as personal preference and political / vendor arm twisting factors involved. I have seen quite a bit installed by developers in subdivisions, but rarely by the agencies for their main transmission or distribution lines.